Las Vegas Metro Public Information Officer Bill Cassell chooses his words carefully while remembering several days in the spring of 1992—not because he’s guarded, but because the events of that week are a blur, fueled by massive stress and lack of sleep. That was the week Las Vegas was on fire, a direct aftermath of the acquittal of the LA police officers involved in the Rodney King beating.

Back then, Cassell was a Metro officer assigned to the K-9 unit. Amid the chaotic scenes he remembers, one in particular haunts him to this day: While other officers were scrambling to assist those in trouble or firefighters who needed cover while putting out fires, Cassell and two other K-9 officers were called to the intersection of Bonanza and Main Street, as a mob of hundreds was making its way down Bonanza. “They had overrun several police roadblocks already,” Cassell remembers. He and his fellow officers got out their dogs and positioned them before the crowd at the end of their 6-foot leashes, snarling, barking and snapping. The sight of the dogs was enough to divert the mob west, where they proceeded to burn several neighborhoods.

“Three cops and three police dogs turned this mob around,” Cassell says. “What would have happened if we had not been there? I am convinced they would have walked up to Main Street, they would have turned right, they would have gone down two blocks, and they would have attacked Downtown. That would have changed the face of Las Vegas, could have changed the face of history. I have every confidence that the security guards down there would not have been as restrained as law enforcement would have been. We could have had a really bad situation.”

Twenty years have passed, but the intensity of that moment is something Cassell and his fellow officers will never forget—and never want to go through again. “I don’t know what it would take to trigger something like that. I hope to God nothing ever triggers anything like that,” he says.

As we all watch events unfold in the Trayvon Martin case—simmering feelings of frustration, protests across the country and vigilantism (whether it’s Spike Lee tweeting the wrong address for George Zimmerman or the Black Panthers putting a bounty on his head)—it seems scarily appropriate to look back on this 20-year-old tragedy. If only as another reminder to learn from our past.